M. Georgi

Assessment of cerebral blood volume with dynamic susceptibility contrast enhanced gradient-echo imaging

Objective Dynamic susceptibility contrast (DSC) enhanced MRI was used to study relative cerebral blood volume (rCBV). Materials and Methods We examined 15 healthy subjects and 47 patients with vascular stenosis or occlusion, with brain infarctions, and with cerebral neoplasms. During bolus injection of Gd-diethylenetriamine pentaacetic acid, a series of rapid T2*-weighted fast low angle shot two-dimensional images were recorded from the same slice. From these images, changes in signal intensity during bolus passage were computed pixel-by-pixel and converted into contrast agent concentration curves. Applying the principles of indicator dilution theory, images of rCBV were calculated. Results and Conclusion Regions of infarctions show almost zero rCBV. In patients with high-grade vascular stenosis or occlusion a bolus delay in comparison to the unaffected side and an increased mean transit time can be observed. Some of the affected areas show an increased rCBV, which is a well-known physiological mechanism that takes place to compensate for the reduced cerebral blood pressure. In brain tumors, rCBV imaging reveals focal or homogeneous areas of increased blood volume. This can even be observed in low-grade astrocytomas with unaffected blood-brain barrier. In CBV imaging, the effects of radiotherapy on tumor tissue can be monitored as a significant decrease of rCBV in tumor tissue after therapy.

Therapy for biliary stenoses and occlusions with use of three different metallic stents: single-center experience.

PURPOSE The authors report their experience with three different metallic stents for the treatment of biliary obstructions during a 6.5-year period (between February 1989 and June 1995). MATERIALS AND METHODS In an uncontrolled, nonrandomized, and prospective study, 168 patients with obstructive jaundice underwent transhepatic placement of metallic stents. Patients were excluded if they were deemed too ill for intervention or had incorrectable coagulopathy. Those patients undergoing external and/or intraluminal radiation therapy, and patients in whom an internal-external catheter was kept in place after insertion of a stent were not included. Inoperable malignant disease was diagnosed in 157 patients (93.5%). Eleven patients presented with a benign biliary stricture that could not be managed by means of angioplasty. One hundred fifty-five Wallstents were placed in 122 patients, 65 tantalum Strecker stents were placed in 30 patients, and 18 Memotherm stents were placed in 16 patients. The patients were followed until September 1996 or until death. RESULTS Regarding malignant obstruction, the 30-day mortality rate was 10.7% without any procedure-related death, and overall survival rates after 100 and 200 days were 63% and 22%, respectively. Regarding benign stricture, eight of 11 patients were alive after a median follow-up of 50.6 months without any 30-day mortality. Major complications occurred in 16 patients (10.2%) who had malignancy, and in two patients (18.2%) with benign biliary disease. The cumulative patency rate in malignant obstructions was significantly higher for the Wallstent than for the Memotherm stent (P < .05) and nonsignificantly higher for the Wallstent than for the tantalum Strecker stent (P > .05). Reintervention due to recurrent obstructive jaundice was necessary in 28 patients (17.8%) with malignancy, and in six patients (54.5%) with benign stricture. CONCLUSIONS The Wallstent is the most effective in achieving long-term palliation in patients with malignant obstructive jaundice. The treatment of benign biliary strictures with metallic stents is associated with a low long-term patency rate.

MR imaging of pancreatic lesions. Comparison of manganese-DPDP and gadolinium chelate.

RATIONALE AND OBJECTIVES To compare manganese-DPDP-enhanced and gadolinium-DTPA-enhanced MR imaging in patients suspected of having pancreatic cancer. METHODS Fifteen patients who underwent MR imaging for suspected pancreatic cancer and received gadolinium-DTPA took part in a clinical phase III trial in which the efficacy of manganese-DPDP for detection of pancreatic cancer was evaluated. T1-weighted gradient-echo (GRE) images with and without fat suppression were used. Signal-to-noise ratio and contrast-to-noise ratio were calculated before and after the administration of each contrast agent. Image quality was assessed using a four-step score; delineation of the normal pancreas was assessed by two readers in consensus. RESULTS In terms of pancreatic signal-to-noise ratio, only gadolinium-DTPA-enhanced fat-suppressed and non-fat-suppressed GRE imaging showed a significant (P < 0.001) increase (72% and 61%, respectively). In the patients with a focal pancreatic lesion (n = 14), a significant increase in contrast-to-noise ratio was found only in manganese-DPDP-enhanced GRE imaging without (106%) and with (82%) fat saturation. Qualitative image analysis demonstrated a significant improvement of manganese-DPDP-enhanced fat-suppressed MR images in delineating the pancreatic parenchyma (P < 0.01) as well as pancreatic tumors (P < 0.01). CONCLUSIONS T1-weighted manganese-DPDP-enhanced GRE imaging with fat saturation should be regarded as the most suitable combination for detecting a pancreatic lesion.

New chest imaging techniques: a comparison of five analogue and digital methods

In recent years new analogue and digital techniques have become available for chest imaging. This study compares conventional film/screen, asymmetric film/screen (InSight), equalization (Amber), storage phosphor and digital image intensifier techniques by phantom exposures and patient examinations. The quality of chest images of 43 patients was classified by seven observers in four different hospitals. According to the results of phantom measurements and a previous study, digital image intensifier radiography was excluded from the patient examinations because of its low image quality. The Amber system had the best image quality. Images of the storage phosphor system were of good quality in both mediastinal and peripheral fields of the chest. Compared to conventional film/screen, the asymmetric film/screen (InSight) was graded higher in the mediastinal field, but lower in the peripheral field.

Evaluation of breath-hold contrast-enhanced 3D magnetic resonance angiography technique for imaging visceral abdominal arteries and veins.

RATIONALE AND OBJECTIVES To evaluate the diagnostic value of breath-hold contrast-enhanced 3D magnetic resonance angiography (MRA) for assessment of the visceral abdominal arteries and veins in patients with suspected abdominal neoplasms. METHODS Twenty-one patients underwent MR imaging on a 1.5 T unit using a body phased-array coil. MRA was performed with a 3D-FLASH sequence (TR 3.8 ms, TE 1.3 ms, flip angle 25 degrees, acquisition time 20 seconds), 8 to 12 seconds after an intravenous bolus injection of Gd-DTPA. The acquisition delay between the arterial and the portal venous phase was 12 seconds. The image quality and the degree of vascular involvement were evaluated using coronal source images and maximum intensity projection reconstructions. Diagnosis was confirmed by surgery/histology. RESULTS Image quality was optimal in more than 85% of the patients (19/21 arterial phase and 17/21 portal venous phase). MRA correctly predicted vascular status in 20 of 21 patients (95%), with complete concordance between MRA results and surgical findings. In one patient with chronic pancreatitis, MRA demonstrated a false-positive finding that could not be confirmed surgically. CONCLUSIONS. Breath-hold contrast-enhanced 3D-MRA is a valuable technique for assessing visceral abdominal arteries and veins.

Transjugular intrahepatic portosystemic shunting (TIPS) with balloon-expandable and self-expanding stents: Technical and clinical aspects after 3 1/2 years’ experience

PurposeTo evaluate prospectively our experience with transjugular intrahepatic portosystemic shunt (TIPS) using four different metallic stents.MethodsBetween November 1991 and April 1995, 57 patients (41 men and 16 women; age 35–72 years, mean 54 years) underwent the TIPS procedure. Techniques for portal vein localization before and during TIPS were fluoroscopy, computed tomography (CT) studies, wedged hepatic venography, arterial portography, and ultrasound. After predilation we deployed balloon-expandable (n=48) and self-expanding (n=45) metallic stents. Fifteen patients underwent variceal embolization. Initial follow-up angiograms (mean 6.9 months, range 3–24 months) were obtained in 39 of these patients.ResultsFifty-three patients (93%) had successful TIPS placement. The mean decrease in portal pressure was 42.7%. Besides fluoroscopy, the most helpful techniques for portal vein localization were venography and CT. Residual stenosis (n=1) and late shortening (n=4) of Wallstents resulted in shunt dysfunction. The technical problems encountered with the Palmaz stent resulted from its lack of flexibility. We combined balloon-expandable and self-expanding stents in 12 patients. The 30-day and late follow-up (mean 11.9 months) percutaneous reintervention rates were 11.3% and 64.2%, respectively. There were no clinically significant complications related to the TIPS insertions.ConclusionAn ideal stent does not exist for TIPS, and the authors recommend combining a Palmaz stent with a flexible self-expanding stent.

Teleradiology requirements and aims in Germany and Europe: status at the beginning of 2000.

Abstract. Specific radiological requirements have to be considered for realization of telemedicine. In this article the goals and requirements for an extensive implementation of teleradiology are defined from the radiological users point of view. Necessary medical, legal and professional prerequisites for teleradiology are presented. Superior requirements, such as data security and privacy or standardization of communication, must be realized. Application specific requirements, e. g. quality and extent of teleradiological functions as well as technological alternatives, are discussed. Each project must be carefully planned in relation to ones own needs, extent of functions and system selection. Topics like legal acceptance of electronic documentation, reimbursement of teleradiology and liability must be clarified in the future.

Proton magnetic resonance spectroscopy in acute, juvenile anorexia nervosa

Anorexia nervosa is usually associated with a shrinkage of the brain that is at least partially reversible with weight gain. The pathogenesis of this brain abnormality is unclear. The purpose of this study was to investigate potential alterations in localized proton magnetic resonance (1H MR) spectra of anorectic patients immediately after an interval of excessive weight loss. Twelve patients and seventeen control subjects were examined. Water suppressed 1H MR spectra were recorded from two voxels placed in the thalamus and in the parieto-occipital white matter. The spectra of ten patients could be evaluated. Comparing patients and control subjects, significantly higher signal intensity ratios of choline containing compounds (Cho) relative to total creatine (Cr) as well as significantly lower ratios of N-acetyl-aspartate (NAA) relative to Cho were found in the white matter region. We hypothesize that these results indicate an abnormal starvation, associated membrane turnover, which predominantly takes place in the white matter. No evidence for neuronal degeneration was found in the thalamus or in the white matter region.

Isolated oculomotor nerve paralysis in Lyme disease : MRI

Abstract Lyme disease is a cause of illness involving multiple organ systems, including, in 10–15 % of cases, the nervous system. Peripheral radiculoneuritis, cranial neuritis, encephalitis and myelitis are among the neurological manifestations found in the second and third stages. We present the MRI findings in isolated oculomotor nerve involvement by Lyme disease and discuss the differential diagnosis.

DOSE AND IMAGE QUALITY OF ELECTRON-BEAM CT COMPARED WITH SPIRAL CT

RATIONALE AND OBJECTIVES To examine dose and image quality of electron-beam CT (EBCT) with continuous volume scan versus spiral CT. METHODS An EBCT scanner was compared with a spiral CT (SCT) scanner. Three phantoms were used to measure low-contrast resolution, high-contrast resolution, slice width, and dose. RESULTS The EBCT scans showed 30% lower high-contrast resolution for most settings. The dose was comparable to that of spiral CT with 3 mm collimation and 76%/106% higher with EBCT for 1.5 mm/6 mm collimation. Low-contrast resolution was comparable to that of spiral CT using 3 mm collimation, slightly worse for 1.5 mm, and bad for 6 mm EBCT collimation (four times higher dose to reach comparable contrast-to-noise ratio). CONCLUSIONS Significant restrictions were found using EBCT with continuous volume scan. The authors found that 3 mm collimation can yield acceptable high-contrast resolution and good low-contrast resolution compared with spiral CT. The use of 6 mm or 1.5 mm collimation needs to be restricted to selected cases.